BACKGROUND: Postpartum haemorrhage (PPH) is a common and occasionally life-threatening complication of labour. Several options for preventing PPH are available, but further advances in this field are important, especially the identification of safe, easy to use, and cost-effective regimes. Tranexamic acid, which is an antifibrinolytic that is used widely to prevent and treat haemorrhage, merits evaluation to assess whether it meets these criteria.OBJECTIVES: To determine, from the best available evidence, whether tranexamic acid is effective for preventing PPH.SEARCH STRATEGY: We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (12 September 2009).SELECTION CRITERIA: All published, unpublished and ongoing randomised controlled trials (RCTs) evaluating the use of tranexamic acid alone or in addition to uterotonics in the third stage of labour or during caesarean section to prevent PPH.DATA COLLECTION AND ANALYSIS: Two review authors independently assessed for inclusion all the potential studies identified as a result of the search strategy. We entered the data into Review Manager software and checked for accuracy.MAIN RESULTS: We included two RCTs. One RCT of unclear quality of 273 women compared tranexamic acid in two doses (0.5 g intravenously and 1 g intravenously) with aminomethylbenzoic acid (0.5 g intravenously) and with no treatment in women who had vaginal birth. We excluded the aminomethylbenzoic acid arm of this trial (92 patients).Another RCT of 180 women who underwent caesarean section compared tranexamic acid (1 g intravenously given 10 minutes before incision) with placebo.Blood loss greater than 400 ml was less common in women who received tranexamic acid after vaginal birth or caesarean section in the dosage of 1 g or 0.5 g intravenously (two studies, 453 women, risk ratio (RR) 0.51, 95% confidence interval (CI) 0.36 to 0.72). Mean blood loss was lower in the group of women who received intravenous tranexamic acid postpartum (two studies, 361 women, mean difference (MD) -75.17 ml, 95% CI -108.23 ml to -42.12 ml).No serious side effects were reported in women who received tranexamic acid in these trials.AUTHORS' CONCLUSIONS: Tranexamic acid decreases postpartum blood loss after vaginal birth and after caesarean section based on two RCTs of unclear quality which reported on only a few outcomes. Further investigations are needed on efficacy and safety of this regimen for preventing PPH.